High temperature dental gold alloy

ABSTRACT

THE PRESENT INVENTION PROVIDES HIGH TEMPERATURE DENTAL GOLD ALLOYS HAVING MELTING POINTS ABOVE 2000*F. AND ADAPTED TO HAVE FUSED THERETO LOW FUSING PORCELAINS HAVING FUSING TEMPERATURES OF ABOUT 1800*F. THE ALLOYS CONSIST OF GOLD, GALLIUM AND PALLADIUM, AND ONE OR MORE ADDITIONAL ELEMENTS SELECTED FROM THE GROUP CONSISTING OF NICKEL, SILVER, PLATINUM AND IRIDIUM. DURING CASTING THE GALLIUM FORMS AN OXIDE ON THE SURFACE OF THE ALLOY WHICH PROMOTES BONDING OF THE FUSED PORCELAIN THERETO WITHOUT DISCOLORING THE PORCELAIN.

United States Patent Oifice 3,574,611 Patented Apr. 13, 1971 3,574,611HIGH TEMPERATURE DENTAL GOLD ALLOY Emil M. Prosen, Bala-Cynwyd, Pa.,assignor to Nobilium Products, Inc., Philadelphia, Pa. No Drawing. FiledNov. 18, 1968, Ser. No. 776,785 Int. Cl. C22c /00 US. Cl. 75-165 7Claims ABSTRACT OF THE DISCLOSURE The present invention provides hightemperature dental gold alloys having melting points above 2000 F. andadapted to have fused thereto low fusing porcelains having fusingtemperatures of about 1800 F. The alloys consist of gold, gallium andpalladium, and one or more additional elements selected from the groupconsisting of nickel, silver, platinum and iridium. During casting thegallium forms an oxide on the surface of the alloy which promotesbonding of the fused porcelain thereto without discoloring theporcelain.

The present invention relates to high temperature gold alloys, andespecially to high temperature dental gold alloys.

Heretofore it has not been possible to fuse porcelain directly to dentalgold for the reason, among. others, that currently available dental goldalloys melt at about 1900 F. and low fusing porcelains fuse at atemperature of approximately 1-800 F, which is too close to the meltingpoint of currently available dental gold alloys to assure stability athigh temperatures and to avoid deformation of shape of the underlyingdental alloy structure when the porcelain is applied by direct fusing.

It is an object of the present invention to provide a high temperaturedental gold alloy which will melt at a temperature in excess of 2400 F.and which when cast will be stable during the application of low fusingporcelain at about 1800 F.

According to the present invention I have found that I can produce ahigh temperature dental gold alloy which melts at approximately 2450 F.and which consists of:

Percent by wt.

Gallium 4 Nickel 6 Palladium 35 Gold 55 I have found that I can producea similar high temperature dental gold alloy which consists of:

Percent by wt.

Silver 1 Gallium 4 Palladium 35 Gold 60 I have also found that 'I canmodify this formula by adding 5% gold and 5% palladium, making acomposition of 110% by weight for the alloy which will have equally hightemperature characteristics.

Generally speaking, the preferred alloy of the present invention willcontain from 2% to 6% gallium, 2% to 12% nickel, and the balancepalladium-gold in the approximate ratios of 35% palladium and 55% gold.Such an alloy will have stability, when cast, and will not deform attemperatures of 2000 F. or higher and will retain its definite shapewhen low fusing porcelain at a fusing temperature of 1800 F. is directlyapplied to such dental gold alloy.

It has been found that such dental gold alloy has an exceptionally highBrinell hardness of as much as 332 under rolled conditions and lendsitself particularly for use in partial castings and partial dentureswherein rigidity in the casting is especially desirable.

It has also been found that the high temperature gold alloys of thepresent invention have extremely high tensile strength and minimalpercent elongation. Both of these characteristics render these alloysespecially desirable for partial dental restorations including partialswhich will accept porcelain application for restoring missing teeth, orfor concealing the underlying metal.

The high temperature melting gold alloys of the present invention have awhite gold color, are extremely hard to the point that they cannot bestamped, and have a tensile strength far in excess of the strengthswhich characterize dental gold alloys currently available. Andfurthermore, as before mentioned, they have sufficient rigidity andstability when cast to withstand the fusing temperatures of low fusingporcelains which can be directly applied to the same.

As a further modification of the present invention, I have found that Ican also provide a high temperature gold alloy which will withstand atemperature of 2000 F. without distortion, which will have the desiredtensile strength and Brinell hardness, and wherein I introduce as anadditional element iridium in approximately equal percentage to gallium.In the preferred formula for the present invention the iridium issubstituted in part for nickel.

I have also found that an alloy consisting, by weight, of approximately88% gold, 8% palladium, 3% platinum, from about 0.25% to 2.00% gallium,and iridium in the same proportion as gallium, possesses the desiredcharacteristics for accomplishing the purpose of the present invention.The iridium in combination with the gold imparts to the alloy thedesired physical properties of tensile strength and Brinell hardness,and also raises the melting point of the gold alloy so as to Withstand atemperature of 2000 F.

In order to incorporate iridium into the gold alloy it is necessary tohave a suflicient percentage of palladium and platinum present to makethe alloy homogeneous, for the reason that platinum and palladium arecompatible with iridium, whereas gold is not. Accordingly, it is notpossible to form an alloy merely by mixing and heating together gold,iridium and gallium. An alloy of said elements will not result for thereason that as soon as that combination is in the liquid state theelements tend to separate. However, if gold is incorporated withpalladium or platinum, or a combination of both, the resulting alloywill accept the iridium and gallium to form the desired alloy. To formthe alloy the iridium, gallium, platinum and palladium are combined andheated until they are completely in solution. This may require atemperature of 2600 F. to 2800" F. When the elements are completely insolution they may be allowed to solidify, after which the desired ratioof gold is added and the mixture is again brought up to its meltingpoint. The four elements, iridium, gallium, platinum and palladium, willinitially float on the surface of the gold. Upon continued heating allof the elements become liquid and go into solution with one another.When the solution becomes clear and no floating particles are visible itis known that the elements are in solution and form the desired alloy,which may then be allowed to solidify.

I have also found as an extremely important additional advantage of thepresent invention that the high temperature alloys herein disclosedallof which contain gallium-provide a thin film of oxide on their surfacewhich is ideal for promoting the fusion of porcelain to such alloyswithout imparting an undesirable color to the porcelain.

'While the present invention has been described in its preferred forms,it will be understood that various changes may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

What I claim is:

1. A high temperature dental gold alloy consisting by weight ofapproximately 55% gold, 35 palladium, 2% to 6% gallium, and anotherelement selected from the group comprising nickel, silver and iridium.

2. A high temperature dental gold alloy according to claim 1, whereinthe other element is from 2% to 12%.

3. A high temperature dental gold alloy according to claim 1, wherein byweight the alloy consists of approximately 4% gallium, 6% nickel, 35%palladium and 55% gold.

4. A high temperature dental gold alloy according to claim 1, wherein byweight the alloy consists of approximately 1% silver, 4% gallium, 35palladium and 60% gold.

5. A high temperature dental gold alloy according to claim 4, to whichhas been added approximately 5% more gold and 5% more palladium.

6. A high temperature dental gold alloy according to 4 claim 2, whereiniridium in the approximate amount by weight of gallium is substituted inpart for nickel.

7. A high temperature dental gold alloy consisting by weight ofapproximately 83% to 89% gold, 0.25% to 2.00% gallium, and 16.75% to 9%platinum group metals selected from the groupcomprising palladium,platinum and iridium.

References Cited UNITED STATES PATENTS 2,050,077 8/1936 Wise 751343,134,670 5/196'4 Prosen 75171 3,134,671 5/1964 Prosen 75172 3,254,2795/1966 Cohn et a1. 75165X 3,340,050 9/1967 Nielsen 75165 3,413,72312/1968 Wagner et a1. 75165X L. DEWAYNE RUTLEDGE, Primary Examiner E. L.WEISE, Assistant Examiner US. Cl. X.R. 75134T, 172

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,57 l6ll Dated April 13, 1971 InventorOi) EMIL M. PROSEN It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

SPECIFICATION:

Column 1, line 63, "palladium-gold" should read palladium gold CLAIMS:

Claim 2, line 10, after "is" insert nickel Signed and sealed this 3rdday of August 1971 (SEAL) Attest:

WILLIAM E SCHUYLER, JF

EDWARD M.FLETCIER,JR.

Commissioner of Patents Attesting Officer

